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TwitterA&A 415, 915-929 (2004)
DOI: 10.1051/0004-6361:20034200
Simulating the recent star formation history in the halo of NGC 5128
M. Rejkuba1, L. Greggio2 and M. Zoccali1, 31 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
e-mail: mzoccali@eso.org
2 INAF, Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy
e-mail: greggio@pd.astro.it
3 Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile and Princeton University Observatory, Peyton Hall, Princeton, NJ 08544-1001, USA
(Received 15 August 2003 / Accepted 6 November 2003)
Abstract
Simulated color-magnitude diagrams are used to investigate the recent
star formation history in NGC 5128. The comparison of the simulations
with the observed
UV color-magnitude diagram for a field in the
north-eastern shell, where recent star formation is present,
constrains the initial mass function (IMF) and the duration of the
star formation episode. The star formation burst is still on-going or
at most has stopped some 2 Myr ago. The look-back time on the main
sequence is set by the incompleteness of the
U-band observations at
, and is of the order of
50 Myr. The post main sequence
phases have a look-back time up to 100 Myr, setting the maximum
observable time for the star formation in this field. The comparison
of the observed and simulated luminosity functions and the number of
post main sequence vs. total number of stars favours models with
active star formation in the last 100 Myr.
),
and are also consistent with slopes in the range of
. They exclude steeper IMF slopes. The mean star formation rate
for a Salpeter IMF in the range of masses
within the last 100 Myr is
.
Key words: galaxies: elliptical and lenticular, cD -- galaxies: stellar content -- stars: fundamental parameters -- galaxies: individual: NGC 5128
Offprint request: M. Rejkuba, mrejkuba@eso.org
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